Oh no. Mirrors or toys may help, yeah! Sometimes it just takes a while to feel comfortable with it. You can try practicing with a toy first, so you are quicker and more confident with the moves, which might help him to relax, too.
Do you hold the top rail tight in your teeth/under you chin while you get the seat sorted? That sort of pins them down a bit. It is very tricky if they don't want to be there! Hopefully you can catch him at a good moment and get it working for you